Carrier Ecologic Series 3 Controls, Start-up, Operation, Service, And Troubleshooting

Also see for Ecologic 30GX080 Series: User manual Controls, start-up, operation, service, and troubleshooting

61Thermistors — To aid in verifying thermistor perfor-mance, resistances at various temperatures are listed for allthermistors (except motor thermistors) in Tables 42A and 42B.See Table 43 for motor thermistor values.LOCATION — General location of thermistor sensors and ter-minal connections in the control box are listed in Table 2.THERMISTOR REPLACEMENTTo replace thermistors T1, T2, T5, or T6 (Entering, LeavingWater; Discharge Gas Temperature):Disconnect appropriate wires from PSIO-2 in unit controlbox. Remove thermistor cable from harness. Remove and dis-card original thermistor from well. Insert new thermistor inwell body to its full depth. Add a small amount of thermal con-ductive grease to thermistor probe and well. Thermistors arefriction-fit thermistors and will slip back into well located atthe cooler head (T1, T2) or at the top of the condenser shell(T5, T6). Secure thermistor to well body with a wire tie toprevent thermistor from working its way out of the well. SeeFig. 22.To replace thermistors T3 or T4 (Liquid Level Sensors):See the Inspecting/Opening Economizers section onpage 53 for information on transferring the refrigerant chargeto the high side. Transfer refrigerant and recover any refriger-ant remaining in the low side.NOTE: A new packing nut and ferrule will be required as theold one is not removable from the old thermistor.For all units, disconnect plug assembly at liquid level sen-sor. Loosen the packing nut fully from the well threads. Re-move and discard old thermistor and packing nut. Slide newpacking nut then ferrule up onto new thermistor probe from in-serted end. Insertion depth is dependent on unit model number.See Fig. 23 and Table 44.Hand tighten packing nut to position ferrule while holdingthermistor in position. With wrench, tighten enough to firmlysecure thermistor in place in well. Run new harness wires intomain control box for 30GX080-176 and all 30HX units. Re-connect blue wires at PSIO-1 for thermistor reading and redwires to TRAN-7. Reconnect plug assembly to new liquid lev-el sensor for 30GX205-265 units. Restore unit control poweronly and verify that level thermistor is reading correctly. Checksystem low side for leaks and repair as necessary. Evacuate lowside and open circuit discharge and liquid valves.To service compressor motor thermistors:Two thermistors are factory installed in each compressor.Connections for the thermistors are located in the compressorjunction box. There are 3 terminals for the thermistors: S1, S2,and C. Motor temperature is measured by leads connected toone of the S terminals and the C terminal. If a compressor mo-tor thermistor failure occurs, verify that there is a true short oropen circuit at these terminals. If one of the thermistors fails,disconnect and relocate the wire on one of the S terminals tothe other S terminal (S1 to S2 or S2 to S1). The thermistorsare not serviceable in the field. If both of the compressor motorthermistors fail, compressor replacement is required. SeeTable 43 for motor thermistor temperature and resistancevalues.Pressure Transducers — A single style of pressuretransducer is used for both high- and low-pressure sensing onthe 30GX,HX chillers. The transducers operate on a 5 vdc sup-ply. The power supply for this is a 24 vac to 5 vdc full waverectified power supply, PS1. See unit component arrangementlabel for mounting location and terminal connections in thecontrol box. Refer to Fig. 24A and 24B for pressure transducerlocations.PRESSURE TRANSDUCER CALIBRATION — Pressuretransducers are factory installed on all models to read Dis-charge, Suction, Economizer (reads leaving condenser pres-sure on models without economizer), and Oil pressure. DONOT attempt to calibrate any of these transducers by the pres-sure gage method unless the transducer is connected to a fullycharged refrigerant system. A more accurate method of cali-bration is used by the 30GX,HX software and corrects forambient temperature when calibrating. Calibrating a transducerwhen the system is under nitrogen charge will result in anincorrect offset being applied to the reading (due to tempera-ture correction). Although these transducers are calibrated atthe factory, replacement transducers require calibration foraccurate readings. Calibration is also required when replacinga PSIO. Access to the transducer calibration area is through theService function and the transducers can be calibrated at thecurrent system pressure using a pressure gage at the samepoint or exposed to atmospheric pressure. In the example inTable 45, the Circuit A Discharge Pressure transducer has beenreplaced and needs to be calibrated. A pressure gage has beeninstalled at the transducer and reads 85 psi (must be in therange of –5.0 to 185.0 psi). See Table 45.The control will apply the 0.8 psi offset from the calibrationexample in Table 45 to all future readings. The calibration pro-cess for any of the other pressure transducers is done in a simi-lar manner. A transducer can also be calibrated at atmosphericpressure by removing the transducer from the system. To dothis, carefully unplug the transducer connector. Unscrew thetransducer from its mounting location and reconnect the con-nector. Follow the steps in Table 45 to read the current pressureand enter 0.0 psig as the gage pressure. Remove the connectorfrom the transducer, thread the transducer back onto the fittingfrom which it was removed (do NOT use thread sealant/com-pound), and reinstall the connector. Maximum offset is 6 psig.If it is necessary, all of the transducers may be calibrated at0.0 psig. All of the transducers must be removed from the sys-tem and reconnected in atmosphere as described. When com-plete, scroll down under to “Calibrate All at 0 PSIG”and press. A “Yes” will be displayed at this step and will auto-matically change back to “No” once all transducers have beensuccessfully calibrated. Reconnect the transducers and connec-tors as described above. All transducers are mounted onSchrader fittings. Therefore, it is NOT necessary to removesystem refrigerant charge. Use a catch pan when removing theoil pressure transducer for calibration as oil will leak outthrough the Schrader fitting.TROUBLESHOOTING — If transducer is suspected of beingfaulty, first check supply voltage to transducer. Supply voltageshould be 5 vdc ± .2 v. If supply voltage is correct, comparepressure reading displayed on keypad and display moduleagainst pressure shown on a calibrated pressure gage. If the 2pressure readings are not reasonably close, replace pressuretransducer.Liquid level thermistors are installed in the top of thecooler using compression fittings. All other thermistors areinstalled in wells and will slide out of the wells easily. Thewells are under refrigerant pressure (cooler EWT and LWTare under waterside pressure) and do not need to beremoved to replace a faulty thermistor.Use care when removing the oil pressure transducers fromthe compressor fitting. The fitting that the transducersmount in is sealed with an O-ring Schrader fitting into thecompressor casting. Do NOT overtighten the transducerwhen replacing after calibration. Hold both fittings withwrenches when removing and reinstalling.